FIG. 1 shows a set of devices 1 to 5 cooperating in a mesh network. In a mesh network each device typically has the capacity to communicate directly with multiple peer devices, without the need to go via an intermediate base station or switch. That can be done using broadcast messages which can be received and actioned by any nearby device, or by messages that are specifically addressed to one or more devices. For example, device 1 can communicate directly with any of devices 2, 3 and 4. Another feature of this mesh network is that devices can serve to forward messages between other members of the network that cannot communicate directly with each other. For example, device 1 can communicate directly with device 2 but not with device 5. Device 2 can communicate directly with device 5. When device 1 wants to send a message to device 5 it can do so by transmitting a message which device 2 then relays onwards to device 5.
It has been proposed that devices may be configured so as to automatically join a mesh network of the type described above when they are in range of other such devices. This may be of particular interest in the field of low powered devices. Emerging protocols such as Bluetooth Low Energy mean that devices capable of wireless communication can be powered for a number of years from a simple battery without the need for recharging. The low cost of these devices, together with the prospect of them having at least as long a lifetime as some common consumer goods, opens up the possibility that the devices could be implanted in a wide range of articles that might be found in a domestic or industrial setting, or that might be carried by a person. Examples include mobile phones, light bulbs, wallets, desks, shopping bags, articles of clothing and door keys. Some of these items may be expected to be static. Others may be moved around. It can be imagined that whatever low power devices happen to be together in one place could adventitiously cooperate to form a mesh transport network. That transport network could relay communications between devices that cannot communicate directly, without someone having to specifically provide underlying infrastructure for the network.
The value of this proposal derives from the possibility that the low cost, low power and long lifetime of the devices can mean that they are so widely distributed that the transport network has a good chance of coming into existence wherever it is needed. However, if the devices devote energy to supporting mesh networks their energy may be depleted and their lifetime may fall. If a network of this type is to be widely adopted it should reach a successful balance between on the one hand devices' propensity to cooperate in networks and on the other hand the devices' lifetimes.
One way to reduce the power consumed by devices cooperating in a mesh network may be to enable them to filter the mesh messages that they process, whilst still relaying them when appropriate. For example, each mesh message could contain a field that indicates some characteristic of the message such as its source, destination or urgency, and a device could decide whether to forward the message based on that field or based on whether the message matches a network key of the node. However, this may not straightforward, because the filtering could itself increase power consumption. Furthermore, in many low power devices receiving signals can use more energy than transmitting signals.
Communication protocols may be implemented using a protocol stack. Protocol stacks are often aligned with the OSI (open systems interconnection) model, in which protocol functions are distributed hierarchically between successive layers in the stack. It may be possible to reconfigure the stack so as to move a function from a higher layer into a lower layer for the purpose of increasing speed or saving power. However, this is generally done for the purpose of directly benefiting the communication needs of the device that has the reconfigured stack.
There is a need for a way of configuring devices so as to increase the potential coverage of adventitious mesh networks.